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The problems are designed to be solved using short APL dfns or tacit functions. If you find yourself writing more than a couple of statements in your solution, you can probably find a better way to do it.
A dfn is one or more APL statements enclosed in braces {}. The left hand argument, if any, is represented in a dfn by ⍺, while the right hand argument is represented by ⍵. For example:
```
      'Hello' {⍺,'-',⍵,'!'} 'world'
Hello-world!
```
A dfn terminates on the first statement that is not an assignment. If that statement produces a value, the dfn returns that value as its result. The diamond symbol ⋄ separates APL statements. For example:
```
      'left' { ⍵ ⋄ ⍺ } 'right'
right
```
For more information on dfns, use the APL Wiki.
A tacit function is an APL expression that does not explicitly mention its arguments. In the example below (+⌿÷≢) is a tacit function which computes the average of a vector (list) of numbers.
```
      (+⌿÷≢) 1 2 3 4 5 6
3.5
```
For more information on tacit functions, see the APL Wiki.
Each problem has a description and one or more examples. Wherever you see your_function is where you should insert your solution (either a dfn or tacit function). Do not add comments to your solutions.
Your code must run in a default Dyalog environment using (⎕ML ⎕IO)←1. If you use other settings for ⎕ML or ⎕IO, they must be local. If you don't know what that means, don't worry, it won't matter to you.
Several of the problem descriptions will describe arguments that can be a scalar (a single element) or a vector (a list). This is largely pedantic, but in such cases your functions should produce correct results for both types of input.
The symbol ⍝ is the APL comment symbol. In some of the examples, we provide comments to give you more information about the problem.

Some of the problem test cases use "boxed display" to make the structure of the returned results clearer. Boxing is enabled by default on TryAPL and can be enabled in your local APL Session with the ]Box user command:

      ⍳¨⍳4
 1  1 2  1 2 3  1 2 3 4 
      ]Box on
Was OFF
      ⍳¨⍳4
┌─┬───┬─────┬───────┐
│1│1 2│1 2 3│1 2 3 4│
└─┴───┴─────┴───────┘